The development of nylons as engineering plastics has a history of almost four decades, but there is still a growing demand for nylons.
There are many basic types of nylon, including nylon 6, nylon 66, nylon 610, nylon 612, nylon 11, nylon 12, copolymers thereof, and blends thereof. Nylons have various inherent characteristics which render them useful for different purposes depending on a particular desired performance characteristic. Based on these characteristics, there continues to be a great demand for nylon products.
Particularly, composites of nylon resins and inorganic reinforcing materials (e.g., a glass fiber) exhibit high mechanical strength and markedly improved heat resistance, and thus they are used as structural materials and interior/exterior materials for automobiles.
However, since nylon resins have a high moisture absorption rate due to their molecular structures, they exhibit dimensional instability and high warpage. Further, the addition of inorganic material to nylon resins causes low impact resistance of the resulting composites.
It is generally known that impact resistance of a composite of a nylon resin and an inorganic material is low because stress accumulates at the interfaces between the nylon molecules and the inorganic material due to low interfacial binding force between the nylon resin and the inorganic material when multiple impacts are applied to the composite. As a result, cracks can occur at the interfaces.
Further, since weak C—C bonds present in the main chain of a nylon resin tend to be cleaved due to the inherent structural characteristics of the nylon resin, it can be difficult to minimize warpage of the nylon resin.
This problem can be solved to some extent by the addition of an inorganic reinforcing material to a nylon resin. Improvement in the warpage of the resulting composite provided by the inorganic reinforcing material, however, is negligible.
Further, although the warpage of the composite is slightly decreased by the addition of the inorganic reinforcing material, a low interfacial binding force between the inorganic reinforcing material and the nylon molecules results in poor mechanical properties (e.g., low impact resistance) of the composite.